It might be a little premature to declare a primary tenet of global warming theory "invalidated" ...

Analysis of rainfall and surface moisture trends have led to a number of studies investigating whether the Earth has been undergoing drying, or whether drying is reversing.

Fellow DailyTech blogger Michael Asher recently reported on one study that analyzed historical rainfall data between 1900 to 2000, and using wavelet analysis concluded that droughts were decreasing, and that major drought events were decreasing as well.

Another study, released just days before by NASA's Goddard Institute for Space Studies (GISS), analyzed the data on rainfall and concluded that worldwide the Earth is undergoing significant drying effects. In particular, much of the Mediterranean area, North Africa and the Middle East are rapidly becoming drier.

The study goes on to use this data to predict current weather patterns.

This study continues a long chain of research which supports a unanimous conclusion that the Earth is experiencing significant drying.

In 2006, the British government funded a climate study carried out by the Met Office Hadley Centre for Climate Prediction and Research.

Its conclusion: global drought increased 25 percent in the 1990s.

It also modeled possible future weather scenarios and found that indicated that extreme drought could affect 30 percent of the world's land surface, up from the current span of 3 percent. Severe drought (the next worse) would rise from 8% land area to 40%, and mild drought would rise from 25% to 50%.

In 2005, the National Center for Atmospheric Research (NCAR), a U.S. government funded research center, released a study that the percentage of Earth's land area stricken by serious drought more than doubled from the 1970s to the early 2000s.

It also found that drought had increased and surface moisture had decreased, on average, worldwide.

Along the lines of the study mentioned in the other Dailytech article, it found that water vapor in the air and global precipitation have increased over the past few decades--however, warming caused the moisture to evaporate at a faster rate, and land moisture levels have been dropping, leading to droughts.

To examine how soil moisture has evolved over the last few decades, the NCAR researchers produced a unique global-scale analysis using the Palmer
index, which for decades has been the most widely used yardstick of
U.S. drought. The Palmer index is a measure of near-surface moisture
conditions and is correlated with soil moisture content.

Interestingly, the study indicated that the U.S. has become wetter over the past 50 years, while most of the rest of the Northern Hemisphere has dried.

While rainfall has increased worldwide, the study found that it has decreased in Africa's Sahel and East Asia, leading to further expansion of dry soils.

The conclusions of these studies: the U.S. may be getting wetter, and rainfall may not be decreasing, but land moisture is definitely decreasing, due to increasing temperatures. Decreased land moisture will lead to more droughts, and more extreme droughts, as the soil experiences further decrease in moisture.

While this is only one element of global warming and climate change theory, it certainly seems premature to declare it "invalidated," as some critics are inclined to proclaim.